The present invention relates generally to a method and apparatus for achieving nitrogen fixation, and more particularly a method and apparatus for achieving nitrogen fixation in a volumetric discharge chamber having a controlled energy to pressure ratio.
Various methods and apparatus for achieving nitrogen fixation are known. Generally air is introduced into an electric discharge chamber, producing an electric discharge along a relatively narrow band. A localized discharge is produced which is directed to only a small portion of the chamber. Nitrogen fixation using a localized discharge requires a high voltage which fluctuates and produces a high energy to pressure (E/p) ratio within the chamber, e.g., usually higher than 25 kV/atm of O.sub.2 /cm. Not only is the E/p ratio high, it is also uncontrollable. Maintenance of uncontrolled high E/p ratios results in the vast majority of the energy being absorbed by oxygen, producing atomic oxygen according to the following equation: EQU O.sub.2 +e.sup.- .fwdarw.20+e.sup.- ( 1)
The atomic oxygen then interacts with nitrogen to produce NO. EQU O+N.sub.2 .fwdarw.NO+O (2)
Reaction (2), however, proceeds at an exceedingly slow rate. Thus the production of NO and hence nitrogen fixation is limited. Typical examples of nitrogen fixation processes which produce a narrow discharge and uncontrollable E/p ratio are disclosed in U.S. Pat. Nos. 1,458,525 and 1,475,995.
The kinetics of reaction (2) can be greatly accelerated by interacting atomic oxygen with nitrogen in the vibrationally excited state, due to a reduction in the activation energy. As used herein, the term vibrationally excited nitrogen means a vibrational temperature equivalent to about 3,000.degree. K. At lower E/p values almost 90% of the energy from the electron beam is absorbed by the vibrational state of nitrogen. However, using a localized discharge of electrons produces a narrow band of electrons in which the E/p ratio cannot be controlled and the formation of vibrationally excited N.sub.2 is minimized.